This study explores how adding cellulose nanofibrils (CNF) which is a renewable, plant-based material can make concrete stronger and more resistant to cracking, especially in cold-weather environments. Cracking due to early-age shrinkage is a major problem that reduces the durability and lifespan of concrete structures.
Abstract: Cracking in concrete structures, particularly under cold-weather conditions, significantly compromises durability and long-term performance. Early-age shrinkage is a primary contributor to crack formation, leading to increased maintenance demands and reduced service life. This study investigates the incorporation of Cellulose Nanofibrils (CNF) as a sustainable additive to mitigate shrinkage and enhance mechanical properties in both cement paste and concrete. Specimens were prepared with CNF dosages of 0%, 0.1%, 0.2%, 0.3%, 0.4%, and 0.5% by weight of cement. In cement paste, CNF addition up to 0.3% improved compressive and flexural strength by approximately 25% and 34%, respectively, and reduced shrinkage by 21%. In concrete, CNF increased compressive strength by 16%, flexural strength by 28%, and reduced shrinkage by 17%. The highest performance was observed at 0.3% CNF, while higher dosages resulted in diminished gains, likely due to fiber agglomeration and dispersion challenges. The results highlight the potential of CNF to enhance the mechanical and durability properties of cement-based materials, offering a promising approach for developing more crack-resistant and sustainable concrete, particularly suited for cold-climate infrastructure applications.
The study focuses on how cross-laminated timber (CLT) and wood fiber insulation perform together in buildings located in cold environments. These materials are gaining popularity as low-carbon, renewable alternatives in sustainable construction, but their long-term moisture and temperature behavior must be understood to ensure durability and safety.
The research team monitored a CLT building in Belfast, Maine, for two years using sensors that tracked temperature, humidity, and moisture levels in the walls and roof. They then used this real-world data to create and calibrate a hygrothermal model, which simulated the building’s performance over five years.
Abstract: The increased complexity of buildings has led to rigorous performance demands from materials and building envelopes. As markets for low-carbon, renewable construction materials grow, cross-laminated timber and wood fiber insulation have emerged as promising alternatives to meet these rigorous demands. However, an investigation into the performance and interaction of materials within high-performance systems is necessary to determine the durability risks associated with increased complexity and the introduction of new materials. This is important in order to ensure that these materials can meet the required functions of the building while taking advantage of their environmental benefits. To do so, this case study investigated a building constructed of cross-laminated timber and wood fiber insulation in a cold climate (Zone 6A) (Belfast, ME, USA). During construction, the building was instrumented with temperature, relative humidity, and moisture content monitoring instrumentation through the envelope, i.e., wall and roof assemblies. The conditions within the envelope were monitored for a two-year period and used to calibrate a hygrothermal model, along with measured material properties. The calibrated model was used to conduct a 5-year simulation and mold risk assessment. Findings demonstrated that there was no moisture or mold risk throughout the monitoring period or simulation. This supports the integration of cross-laminated timber and wood fiber insulation in sustainable building practices, particularly in cold climates where moisture management is critical.
Effect of Fiber Type on the Thermomechanical Performance of High-Density Polyethylene (HDPE) Composites with Continuous Reinforcement.
ASCC researchers José Luis Colón Quintana, Scott Tomlinson, and Roberto A. Lopez-Anido recently published an article in the Journal of Composites Science. The study investigates how glass fiber (GF) and ultra-high-molecular-weight polyethylene (UHMWPE) fibers affect the thermal, mechanical, and viscoelastic performance of HDPE composites, particularly in extreme environments relevant to defense applications. Using methods such as differential scanning calorimetry, thermomechanical analysis, and dynamic mechanical analysis, the team evaluated material behavior across a range of realistic conditions.
Abstract: The thermal, thermomechanical, and viscoelastic properties of continuous unidirectional (UD) glass fiber/high-density polyethylene (GF/HDPE) and ultra-high-molecular-weight polyethylene/high-density polyethylene (UHMWPE/HDPE) tapes are characterized in this paper in order to support their use in extreme environments. Unlike prior studies that focus on short-fiber composites or limited thermal conditions, this work examines continuous fiber architectures under five operational environments derived from Army Regulation 70-38, reflecting realistic defense-relevant extremes. Differential scanning calorimetry (DSC) was used to identify melting transitions for GF/HDPE and UHMWPE/HDPE, which guided the selection of test conditions for thermomechanical analysis (TMA) and dynamic mechanical analysis (DMA). TMA revealed anisotropic thermal expansion consistent with fiber orientation, while DMA, via strain sweep, temperature ramp, frequency sweep, and stress relaxation, quantified their temperature- and time-dependent viscoelastic behavior. The frequency-dependent storage modulus highlighted multiple resonant modes, and stress relaxation data were fitted with high accuracy (R2 > 0.99) to viscoelastic models, yielding model parameters that can be used for predictive simulations of time-dependent material behavior. A comparative analysis between the two material systems showed that UHMWPE/HDPE offers enhanced unidirectional stiffness and better low-temperature performance. At the same time, GF/HDPE exhibits lower thermal expansion, better transverse stiffness, and greater stability at elevated temperatures. These differences highlight the impact of fiber type on thermal and mechanical responses, informing material selection for applications that require directional load-bearing or dimensional control under thermal cycling. By integrating thermal and viscoelastic characterization across realistic operational profiles, this study provides a foundational dataset for the application of continuous fiber thermoplastic tapes in structural components exposed to harsh thermal and mechanical conditions.
In situ growth of mycelium in a lignocellulosic scaffold enabled by cellulose nanofibrils for lightweight insulation
ASCC researchers Mehdi Tajvidi,Maryam El Hajam and Caitlin Howell along with colleagues Wenjing Sun from Cranfield University and Islam Hafez from Oregon State University, recently published an article in Applied Science and Manufacturing. This study explores how mycelium, a natural fungus, can be grown inside a lightweight foam scaffold made from plant-based fibers and cellulose nanofibrils (CNFs). The goal is to create sustainable insulation materials that could replace petroleum-based options like polystyrene. This work matters because it shows that mycelium-based composites could be used in construction and packaging as eco-friendly, resource-efficient alternatives to plastic foams
Abstract: Mycelium-lignocellulosic fiber composites (MLFCs) offer a promising sustainable alternative to lightweight, petroleum-based materials and are gaining significant interest across various sectors. However, creating low-density MLFCs that provide superior thermal and sound insulation properties along with good mechanical strength remains a substantial challenge. In-mold packing is the primary fabrication process explored so far for MLFCs, limiting the ability to design complex shapes, and expanding potential applications. Growing mycelium on pre-produced low-density lignocellulosic foam scaffold substrates is an innovative process that represents a promising, yet underexplored, approach for MLFCs. This approach offers the potential for design flexibility and enhanced structural properties. In this study, hybrid low-density foams made from lignocellulosic fibers, cellulose nanofibrils (CNFs), and mycelium (Trametes versicolor) were developed and assessed as foam-like insulation materials. A foam-forming method enabled by a surfactant was used to prepare low-density foam scaffold substrates from hardwood and softwood fibers with CNFs as a binder. The raw scaffold substrates and the final MLFCs were characterized for thermal conductivity, sound absorption, water resistance, mechanical strength, and morphological properties. The composites demonstrated excellent thermal insulation, soundproofing, and mechanical strength, as well as thermal and sound properties comparable to or even better than expanded polystyrene (sound absorption coefficient > 0.9 at 1600 Hz). Overall, the results showed that MLFCs have strong potential for further exploration in semi-structural applications, such as lightweight insulating infill panels and protective packaging, offering environmentally friendly and resource-efficient solutions for the construction insulation and packaging markets.
Advancing the use of Cellulose nanofibrils (CNF) in 3D printing via microwaves
A publication by UMaine researchers, Md Musfiqur Rahman and Mehdi Tajvidi, alongside Oregon State’s Islam Hafez was published in Celluloseon July 10, 2025. The study presents a method to make the use of Cellulose nanofibrils (CNFs), a sustainable alternative for 3D printing when compared to petroleum-based polymers, more efficient. The presented method makes use of urea and carboxymethyl cellulose (CMC) as additives enabled by microwave irradiation to solidify the printed structures, which eliminates the need for energy-intensive freeze-drying or oven drying. The research shows that this method, as stated in the abstract, “provides an economically viable option to promote sustainable nanomaterials in the field of additive manufacturing and paves the way for further development.”
Abstract: Cellulose nanofibrils (CNFs) offer a sustainable alternative for 3D printing applications when compared to petroleum-based polymers. However, the significant amount of water in CNF suspension limits their application due to the need for lengthy and energy-intensive drying technologies. This study presents a novel process for the 3D printing of CNFs using urea and carboxymethyl cellulose (CMC) as additives enabled by microwave irradiation. Additionally, this process eliminates the need for freeze-drying or conventional oven drying methods. Two multilayer geometries were constructed: octagonal shells and cuboids with 100% infill. The 3D-printed paste was first solidified by freezing followed by immediate thawing through microwave irradiation. The amplitude-sweep and zeta potential analyses revealed information on the effect of urea and CMC on the printability of CNFs. The compressive testing results indicated that structures containing 2 pph (Parts per hundred) CMC exhibited higher compressive strength than the structures with 1 pph CMC, regardless of the urea concentration. Additionally, the high CMC content enhanced the interfacial adhesion between the layers. In addition, a thorough investigation of the chemical interactions among CNF, urea, and CMC was conducted using Fourier-transform infrared spectroscopy (FTIR). This distinct approach for 3D printing, based on the use of CNFs and microwave irradiation, provides an economically viable option to promote sustainable nanomaterials in the field of additive manufacturing and paves the way for further development.
Toolbox created for efficient towing of Floating Offshore Wind Turbines
An article by ASCC and UMaine researchers, Amrit Shankar Verma, Anthony M. Viselli, and Christopher Allen, and Samuel Davis from Regeneron Pharmaceuticals was published in the Journal of Offshore Mechanics and Arctic Engineeringon July 7, 2025. This research presents a toolbox for planning towing operations for floating offshore wind turbines. The methodology within the toolbox allows users to predict towline tension and estimate bollard pull requirements. The study tests the toolbox’s predictions by comparing them to measured data from the University of Maine’s VolturnUS 1:8 deployment, showing that it can accurately forecast static and dynamic towline tensions. The toolbox also includes a feature for site-specific weather window analysis, which helps in determining optimal conditions for safe and efficient towing.
Abstract: The floating offshore wind industry is poised for growth with advancing technologies and expanding commercial projects. Towing is a key marine operation in offshore wind, where safety and efficiency depend on selecting a suitable tug, tow speed, and predicting towline tensions in a variety of sea states. Accurate tension predictions aid in efficient towing system design, while site-specific weather analysis is crucial for planning and safety. The present paper describes a methodology for towing dynamics predictions and is implemented into a toolbox for planning future operations. The proposed methodology is able to (a) estimate the bollard pull requirements and static towing forces crucial for planning a tow operation; (b) predict the mean and dynamic towline tensions in a given sea state; and (c) integrate a weather window analysis to determine operational statistics. Three separate analyses are presented. In the first analysis, the towline tension estimates from the toolbox are validated against measured tension data from the University of Maine’s VolturnUS 1:8 deployment. In the second, a parametric study is performed using the toolbox and presented for a 6 MW FOWT. In the third, an operability analysis is presented for a Gulf of Maine lease area where two methods are used to calculate weather windows. The results of the study show the toolbox was able to closely predict the measured static and dynamic towline tensions. The weather window analysis shows the capabilities of the toolbox for performing weather window calculations using the results of the physics based calculations.
Field-Bendable Thermoplastic Composite Rebar Created with the Continuous Forming Machine (CFM)
A recent publication by Vanasse Hangen Brustlin Inc. engineer and UMaine alum, Andrew P. Schanck, and University of Maine researchers, Jacob C. Clark, William G. Davids, Roberto A. Lopez-Anido, and Cody A. Sheltra was published in the Journal of Composites Science on July 18, 2025. The research focuses on creating an alternative to traditionally used steel reinforcing bars that is both corrosion resistant and field-bendable. This alternative, made with fiber-reinforced thermoplastic polymers (FRTP), is formed using the Continuous Forming Machine (CFM). Simple bend tests are performed to verify its ability to be field-formed. Although further improvements still need to be made, the research shows that FRTP rebars formed by the CFM are a viable alternative to traditional steel rebars that could significantly improve the long-term integrity of concrete structures and simplify construction processes.
Abstract: Despite the strength and ductility of steel reinforcing bars, their susceptibility to corrosion can limit the long-term durability of reinforced concrete structures. Fiber-reinforced polymer (FRP) reinforcing bars made with a thermosetting matrix offer corrosion resistance but cannot be field-bent, which limits flexibility during construction. FRP reinforcing bars made with fiber-reinforced thermoplastic polymers (FRTP) address this limitation; however, their high processing viscosity presents manufacturing challenges. In this study, the Continuous Forming Machine, a novel pultrusion device that uses pre-consolidated fiber-reinforced thermoplastic tapes as feedstock, is described and used to fabricate 12.7 mm nominal diameter thermoplastic composite rebars. Simple bend tests on FRTP rebar that rely on basic equipment are performed to verify its ability to be field-formed. The manual bending technique demonstrated here is practical and straightforward, although it does result in some fiber misalignment. Subsequently, surface deformations are introduced to the rebar to promote mechanical bonding with concrete, and tensile tests of the bars are conducted to determine their mechanical properties. Finally, flexural tests of simply-supported, 6 m long beams reinforced with FRTP rebar are performed to assess their strength and stiffness as well as the practicality of using FRTP rebar. The beam tests demonstrated the prototype FRTP rebar’s potential for reinforcing concrete beams, and the beam load–deformation response and capacity agree well with predictions developed using conventional structural analysis principles. Overall, the results of the research reported indicate that thermoplastic rebars manufactured via the Continuous Forming Machine are a promising alternative to both steel and conventional thermoset composite rebar. However, both the beam and tension test results indicate that improvements in material properties, especially elastic modulus, are necessary to meet the requirements of current FRP rebar specifications.
Ayan Dutta and William M. Gramlich recently published an article with ACS Publications,analyzing the conditions to which thiol-norbornene hydrogels can spontaneously gel; providing useful information to explain a previously unexplainable phenomenon. Industries such as drug delivery, tissue engineering, and regenerative medicine rely heavily on hydrogels, and this research allows for opportunities for more efficient use of hydrogels.
Abstract: Typically, externally triggered initiators are required for norbornene-modified polysaccharides to undergo thiol–ene gelation into a hydrogel. However, anecdotal and reported evidence exists of these prehydrogel solutions undergoing spontaneous thiol–ene gelation without the trigger. Understanding the origin of this spontaneous process would improve the storage of prehydrogel solutions. We found that polysaccharides with carboxylic acids (e.g., carboxymethyl cellulose) can overcome the buffering capacity of phosphate-buffered saline (PBS), creating an acidic solution that is required for spontaneous gelation. Investigation using a small molecule model system revealed that acidic pH and trace metal ions increase the reaction rate and the conversion to the thiol–ene product. We concluded that the self-initiated thiol–ene reaction resulted from a Fenton-like reaction catalyzed by trace metal impurities, such as iron(II), that generate reactive oxygen species (ROS) that initiate the reaction. Using this knowledge, we developed strategies to inhibit spontaneous gelation and increase the working time of prehydrogel solutions.
Predicting the Strength of Gyroid Infill Structures for 3D Printing
ASCC researchers Phillip Bean, Senthil S. Vel, and Roberto A. Lopez-Anido recently published a study in Progress in Additive Manufacturing to determine the nonlinear behavior and yield strength of gyroid infill structures. Read more from the Maine College of Engineering And Computing.
Abstract: A combined numerical and experimental approach is implemented to determine the effective yield strength of additively manufactured gyroid infills. A representative volume element of the infill geometry is discretized using solid elements and analyzed using the finite element method with an elastic–plastic constitutive model. The effective compressive and shear yield strengths of the cellular material are obtained for varying infill densities through compressive and shear deformations of the representative volume element under periodic boundary conditions. The numerically obtained compressive and shear yield strengths compare well with experimental data for gyroid infill prototypes manufactured using a polymer extrusion-based 3D printer. The numerical predictions are used to develop a simple semi-empirical relationship for the effective yield strength as a function of the relative density. This relationship is expected to be useful in design workflows utilizing the gyroid infill, specifically those involving topology optimization Keywords: Additive manufacturing; 3D printing; Finite element analysis; Gyroid
Structural Properties of Foam-Formed Lignocellulosic Materials
Researchers Rakibul Hossain, Maryam El Hajam, Islam Hafez, and Mehdi Tajvidi published an article in Construction and Building Materials, exploring the possibilities of using plant based fibers and manufacturing them into sustainable, lightweight materials. The process is called foam forming, and it uses natural fibers mixed with air bubbles and water. The product is a light, foamy substance that dries into a resistant and porous structure. The team experimented with different processing methods to see how the strength and structure changed in the dried foam. Studying natural fibers and their properties and applications can help find sustainable alternatives to plastics that are used in everyday life, allowing for scientists to create recyclable, biodegradable products.
Abstract: This study provides a comprehensive understanding of the production of surfactant-assisted cellulose nanofibril (CNF)-reinforced thermomechanical pulp (TMP) fiber-based dry foams via the wet foam forming process. The synergistic interactions between TMP fibers, CNFs, and sodium dodecyl sulfate (SDS) surfactant to optimize foam stability during the wet foam forming process, and their impact on the properties of dry foam samples were comprehensively studied. Furthermore, investigating the effect of surfactant, CNFs, and TMP fibers on the foamability, foam volume stability, and foam liquid stability revealed information on the mechanisms by which various components affect the foam forming process. This understanding enabled tailoring and optimizing the properties of dry foams, such as density, inter-fiber distance, porosity, and fiber orientation. Microstructural analysis revealed that all these parameters significantly influenced foam thermomechanical properties. By controlling surfactant concentration, CNF content, and solids level, foams with densities ranging from 16 to 104 kg/m³ and porosities between 93.1 % and 98.9 % were produced. Foams of different formulations demonstrated low thermal conductivity (0.033–0.043 W/m.K), comparable to other reported biobased and synthetic foams. Foams exhibited excellent compressive strength, with formulations containing 10 % CNFs at 10 % solids with 2 g/L SDS meeting Type XI expanded polystyrene (EPS) insulation standard requirement (35 kPa at 10 % strain). Notably, the foams showed outstanding thickness recovery (up to 100 % after 24 h) and sound absorption coefficients matching or exceeding commercial petroleum-based foams, with maximum absorption achieved at 2500 Hz. Paper lamination further enhanced flexural properties, increasing modulus of rupture by 55–71 %. These fully biobased foams, which require no additional petrochemical binders, demonstrate the potential to effectively replace petroleum-based foams in building and packaging applications, offering a sustainable solution with robust performance.Keywords: Lignocellulosic materials; Foam forming; Insulation; Surfactant; Cellulose nanofibrils
Electrospun Polymer Fibers and Electromagnetic Interference Shielding
Colton Duprey, Theodore Warfle, and Evan K. Wujcik recently published an article in Advanced Engineering Materials, studying electrospun polymer fibers and their applications in electromagnetic interference (EMI) shielding. EMI is an undesirable disturbance that is caused by electromagnetic waves, which negatively impacts electronic device performance. As these devices are getting smaller and more powerful, EMI poses a bigger concern. Older EMI shielding materials are stiff and heavy, whereas spun fibers with MXenes are flexible, lightweight, and efficient. MXenes are 2D nanomaterials that have excellent conductivity, mechanical strength, and hydrophilic properties.
Abstract: The increase in electronic devices that communicate via electromagnetic waves has amplified concerns about electromagnetic interference (EMI), highlighting the need for efficient, lightweight, and flexible shielding materials. Traditional metal-based shields are effective but suffer from drawbacks, including rigidity, high weight, and secondary EM pollution due to reflection. Electrospun nanofiber composites offer a promising alternative, attenuating EM waves through internal scattering and multiple reflections within porous, flexible mats. The inclusion of conductive additives enhances shielding performance even at considerably lower loading percentages. One particular additive has demonstrated an excellent propensity to form lightweight, multilayered nanofiber composites with high attenuation. MXenes, a 2D material with high electrical conductivity and high permittivity to promote reflection and absorption have become a trend in EMI shielding. Their ease of dispersion in polymer matrices enables shielding with minimal weight, while also reinforcing mechanical properties. This review explores recent progress in nanofiber-based EMI shielding, emphasizing the role of MXenes in enabling high-performance, ultrathin, and flexible shields. Key advantages, current limitations and challenges, and prospects are discussed. This review seeks to offer insight into state of nanofiber-based composites for EMI shielding and discuss the advantages and limitations of MXenes in the innovation of next-generation EMI shields.
Using Douglas Fir Biochar for Controlled Release Fertilizer
Xuefeng Zhang co-authored a publication in Soil Advancesexamining douglas fir biochar and its applications as a fertilizer. Biochar is a charcoal-like substance made from wood waste, like douglas fir, which is an abundant byproduct in the forestry industry. University of Maine and Mississippi State University researchers loaded the biochar with nutrients and tested its efficacy as a fertilizer. The porous structure of biochar was found to be ideal for holding water and nutrients and releasing them slowly. Controlled release fertilization is crucial for both farmers and the environment; it reduces nutrient runoff and lowers the frequency of fertilizer use. This innovative application of Douglas Fir could be notably valuable in Maine, creating an eco and budget-friendly solution for local farming.
Abstract: Numerous agricultural soils may lack essential macronutrients crucial for plant growth. Utilizing highly water-soluble commercial fertilizers over extended periods can be both expensive and ecologically unfavorable. Herein, we developed nitrogen (N), phosphorus (P), potassium (K), and magnesium (Mg)-enriched Douglas fir biochar (BCF) as an eco-friendly and cost-effective fertilizer for plants. The BCF was synthesized by precipitating MgNH4PO4.6 H2O and MgKPO4.6 H2O on the biochar surface, which was characterized using XRD, XPS, SEM, and elemental analysis. BCF contained 43.76 ± 3.26 mg g−1 of NH4+ (3.40 ± 0.25 as N%), 120.14 ± 5.95 mg g−1 of PO43- (8.98 ± 0.31 as P2O5%), 3.79 ± 0.58 mg g−1 of K+ (0.41 ± 0.01 as K2O%), and 34.05 mg g−1 of Mg2+. The releasing behaviors of NH4+, PO43-, K+, and Mg2+ were investigated through a series of batch leaching experiments at different pHs (1−13), different water matrices, and three different temperatures (5, 25, and 40 °C), as well as fixed-bed continuous flow column experiments. Finally, greenhouse studies were carried out to study the performance of BCF fertilizer as a slow-release P fertilizer for corn growth. In comparison with conventional P fertilizer and the simple blends biochar (BC) and P fertilizer, the use of BCF yielded ∼23 % higher plant heights on the 35th day, ∼64 % higher plant dry weight, and ∼111 % higher P uptake compared to triple superphosphate fertilizer at 29.70 kg (P2O5) ha−1 nutrient rate for corn growth.Keywords: Biochar; Struvite; Struvite-K; Controlled release; Fertilizer; Corn
3D Printed Sand Texture and Density Improvements for Modeling
Samuel R. Morris & Philip F. King published an article in the International Journal of Metalcasting, examining the orientation of the 3D printer head and its effect on sand density and surface texture in metal casting molds. The paper concludes that the density of printed sand varies based on the direction the printer head is moving, and that surface roughness can change by up to 13%. This directly affects the metal flow and solidification of the metal, causing imperfections. By noticing these variations in texture and density-known as anisotropy, modeling can hopefully account for it in future casting.
Abstract: Within the field of 3D sand printing, there is a growing need to understand the anisotropic behavior of sand in the build envelope of 3D sand printers. For metal casting, this understanding will improve mold accuracy and design. This work provides methodologies to characterize printed sand’s density and surface texture as related to orientation within a printer build envelope, two properties that directly impact liquid metal flow and solidification. Density of printed sand samples was found to vary based on the travel direction of the printer recoater. Surface roughness was found to be influenced by multiple factors, each changing the surface roughness by up to 13%. These findings highlight the importance of considering anisotropy in the design of 3D printed sand molds. The methodologies developed in this study provide a foundation for future research aimed at improving the modeling of complex 3D printed sand molds. Keywords: Additive manufacturing; 3D sand printing; 3SDP; Material Properties; Process modeling; Mold design
